The repair of the vacuum element, by replacing the diaphram, is only done for the 80 and prior models. After 1980 ( don't hold me to that date, may be 79) you just replace the unit with a new one. They are not that expensive and do you really want to "glue" it and have to go back in the dash again in a couple of weeks/months??????

http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1I8107Q051I8107UPU&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1983&product=O4010-70075&application=000377396

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car